Budget Management of In-Ground Costs

Precast concrete components provide a variety of savings to a project in ways that are not always considered when looking at upfront costing versus other materials, including masonry block and curtain wall. These savings include:

1. Speed

Precast concrete components provide a variety of ways to speed the construction process, from design through fabrication and erection. These efficiencies can shave as much as one third of the time needed for construction, meeting tight deadlines and generating revenues quicker. Time can be saved through:

The design process. It takes less time to design a precast concrete building than one built of masonry, due to the lessened detail required in precast's panelized system and the ability to quickly replicate both structural and architectural components.

The fabrication process. Precast components can be fabricated while permitting and foundation work progress, so they are ready to begin erection as soon as foundations are complete. As a single-source supplier for a large portion of the structural system, precasters help maintain the critical-path scheduling.

The erection process. Foundations can be placed one day and precast load-bearing panels or structural framing can be erected as soon as the foundations have cured sufficiently. Wall panels, double tees and hollow-core planking also erect quickly, often cutting weeks or months from the schedule. This speed allows construction to get into the dry quicker. The fast enclosure also lessens concern for weather or material damage during erection, reducing the contractor's risks and costs.

The finishing process. Precast concrete insulated sandwich panels create a finished interior wall that avoids the time and cost of furring and drywalling. Architectural panels can have a variety of colors and textures cast into them, including several in one panel, eliminating the need to field-set trim pieces or paint the facade after the structure is built.

2. Design Economy

The custom, sculptured designs that are possible with precast concrete may be achieved within a limited budget by selecting economical aggregates and textures combined with effective production and erection procedures. The key factors in designing economically with architectural precast are:

Repetition. By reusing the same dimensions for components, the same forms can be used, minimizing the total number needed and the changes between castings.

Effect of Repetition on Panel Square-Foot Cost

Number of reuses

Panel size (square feet)

Mold Cost

Cost per square foot

1

200

$3,000

$15.00

10

200

$3,000

$1.50

20

200

$3,000

$0.75

30

200

$3,000

$0.50

Source: DN-11-02: Designer’s Notebook: Design Economy.

Project Price Changes Based on the Number of Forms Affected by a Complex Shape

Pieces

Project total (square feet)

Forms affected

Project premium

Premium per square foot

100

12,500

1

$4,000

$0.32

100

12,500

2

$8,000

$0.64

100

12,500

3

$12,000

$0.96

100

12,500

4

$16,000

$1.28

Source: DN-11-02: Designer’s Notebook: Design Economy.

Average piece size. Precast pricing is determined primarily by the size of the pieces and piece repetition. Pricing depends more on the number of pieces than the size of the project. Labor functions drive pricing more than material cost, and each new piece of a different size or shape drives up that cost.

Effect of Panel Size on Erection Cost per Square Foot
(based on a minimum erection time of one month)

Panel size(square feet)

Erection Cost per Piece, $/square foot

$300

$600

$900

$1,800

50

6.00

12.00

18.00

36.00

100

3.00

6.00

9.00

18.00

150

2.00

4.00

6.00

12.00

200

1.50

3.00

4.50

9.00

250

1.20

2.40

3.60

7.20

300

1.00

2.00

3.00

6.00

Source: DN-11-02: Designer’s Notebook: Design Economy.

Lump Sum Price Versus Piece Size

Square foot per piece

Cost per piece

Cost per square foot

100

$3,000

$30.00

150

$3,500

$23.22

200

$4,000

$20.00

Source: DN-11-02: Designer’s Notebook: Design Economy.

Material Efficiency. Precast concrete saves money by replicating the look of more expensive materials, such as natural stone (granite, marble, limestone, sandstone or slate). Veneers of these materials also can be cast into the face of the precast components, saving the expense of full thickness pieces. Brick-faced precast also eliminates labor costs and speeds up construction.

Construction Efficiency. Because precast components are fabricated under factory-controlled conditions at a plant, harsh winter weather does not impact the production schedule or product quality. This approach means they can be erected through the winter months to meet a tight schedule, cutting overhead costs and opening the building for occupancy faster.

Hidden Costs. Precast concrete’s speed of construction can reduce the construction timeframe by several months. This results in less time to carry financial bonds, lower contractor overhead costs and risk, elimination of expenses for non-precast related equipment and reduced subcontractor costs by giving more responsibility to a single-source supplier.